Tetracycline (a well known antibiotic)  is harmful to our normal body. Scientist have unrevealed the mechanism. Kindly see the cartoon on it.

Link to original research paper:  http://www.cell.com/cell-reports/pdf/S2211-1247%2815%2900180-1.pdf

Link to general article on web: http://www.the-scientist.com/?articles.view/articleNo/42414/title/Widely-Used-Antibiotics-Affect-Mitochondria/